This Instructable will cover how to 3D model inside of Blender, specifically for 3D printing. As an example model, we are going to bring back our old friend Clippy!

We will be covering:

Working with Bezier Curves
Creating and editing meshes
Edge Split and Subdivision Surface modifiers
Boolean Modifier
Exporting

Supplies

Files on Github: https://github.com/ExplodedViewProjects/Clippy

Ingredients

Black Filament (https://amzn.to/36rg99C)
White Filament (https://amzn.to/36s6Juk)
Grey Filament (https://amzn.to/2XrDYKh)
Super Glue (https://amzn.to/3gpo2B8)

Tools

Sandpaper (https://amzn.to/2X0LX1W)
3D Printer

Step 1: Setup Blender

Install and open up Blender. It can be downloaded from blender.org, is completely free, and will work on any operating system. It will open with a default cube. Hit A to select everything, the X to delete everything that is selected. Then, go into Top view by pressing 7 on your number pad

To add a reference image, press SHIFT + A and select Image > Background Image. Download an image from the internet and add it in.

Step 2: General Clippy Shape

Clippy is a nice curvey shape. Because of this, we can use a curve to make the shape. Add a Bezier Curve with SHIFT + A > Curve > Bezier Curve.

Press TAB to edit the curve and use S to scale it down. Now you can adjust the curve by selecting the centre of each control handle and moving it around with G. You can rotate it with R or control how aggressively the curve passes through that point by scaling the control points using S. You can adjust the angle out each side or how aggressively it curves by moving a single handle. Select one handle, then use G to move it around. Move and adjust the handles to align the curve with Clippy in the background.

To make a section of curve more detailed, you can select two neighbouring control points, right-click, and choose Subdivide. That will put a new point in the middle of the section. To extend the curve so it is longer, choose one of the end points, and press E. That will extrude a new control out the end of the curve.

Step 3: Give Clippy Some Weight

Once the curve approximates Clippy, we need to give it some thickness. On the right side, you can choose the Curve tab. Under Geometry, add a bevel. This will give the curve some thickness. A value of 0.5 works well for this image, but may need to be different depending on the image you are using.

Go through and clean up the curve now that it has some thicnkess You need to close the ends of the curve so it is a closed body. If you don't do this, it won't be able to print it. There is an option under the curve called "Fill Caps". This used to work, but isn't at the time of making this Instructable. Not sure if it's something I'm forgetting, or if it's a bug.

Step 4: Make the Body a Mesh

Now to turn it into a mesh that you can actually use for printing, go Object > Convert to > Mesh from Curve. That will create a series of vertices that approximate the curve that you created.

Now we can close off the ends. Hold down ALT to select the ring around the end, then press E to extrude it. Scaling by 0 will scale all of those vertices together. Now you can hit A to select everything, right-click and select Merge Vertices > By Distance. That will remove all of the duplicate vertices that you have on the ends.

If you look closely, notice that the ends look kind of rounded. That is because the smoothing is trying to make it look like one nice clean face, but you actually want nice sharp edges there. What we're going to do is force those edges to actually be duplicated so the smoothing doesn't try to clean them up. Open the modifier tab (the little wrench) and add am Edge Split modifier. Modify the split angle so the ends have hard edges, but the main mesh looks smooth.

To make the mesh nice and smooth for printing, also add a subdivision surface modifier. This will break up all of the faces into smaller faces in a nice smooth way. This will add a lot more geometry to your model so the file will be bigger, but it will be more detailed and will print a lot nicer.

Step 5: Eyes on the Prize

Next, add the eyes. Press SHIFT + A and select Mesh > UV Sphere. There are two different types of spheres, UV and Ico. The only difference is how the vertices are laid out by default. A UV sphere has concentric rings that go all the way around it, which works really well for eyes because you have a pupil which is a circle inside of the eye which is another circle.

Once you've added the body move the body, move it so it's centered on the eye, then rotate the body so it's roughly in line with where the eye is angled. Do this in object mode. You are modifying the object's location, so X will be sideways relative to the eye, not to the world. Press TAB to enter edit mode and then scale along local Y. To do that, press Y twice. Pressing Y once would scale in global Y, but Y twice will scale along the Y of the eye, which has been rotated. Also scale it along X an Z to get it the right shape, then move it up to it sits out front of the main body.

In edit mode, hold down ALT to select a ring around the pupil, and everything inside it. Once it is selected, press P and choose Selection. This will split the pupil out into its own mesh so it can be printed separately. With the main eye shape done, press SHIFT + D to duplicate the eye to make the other one. Move it into position with G.

Because we are using 2.8. we can edit multiple meshes at the same time. You couldn't do this with previous versions. Edit the pupils. Select everything with A, then hit E to extrude. That will let you pull the newly extruded vertices down into the eyeballs. Once they are pulled in, press S to scale, then 0. That will make them nice and flat so they don't have any curvature.

Do the exact same thing with the eyes themselves. Edit the eyes. Select around the edge where the pupils are by holding ALT, then press E to extrude. You will want to enable vertex snapping at the top of the window. This will let you snap to the bottom of the pupil, making sure the two line up nicely. Press G + Z to move the newly extruded edge down in Z, and mouse-over the bottom of a pupil. The edge will snap to that depth. Once the edge is at the correct depth, change your Transform Pivot Point to Individual Origins. Hit E again then scale (S) and 0 to close off the bottoms. As usual, remove duplicated by distance.

Select one piece of the eyes and add an Edge Split modifier and a Subdivision Surface modifier. That will make nice sharp edges and add geometry. This won't add those modifiers to all pieces of the eye though. Select all of the other bodies that you want to have the same set of modifiers and make sure to select the body you already setup last. That makes it the active element. Now you can press CTRL + L, which will link any features of the active element to the other bodies. Select Modifiers. This will set up all of the other bodies to have the same set of modifiers that the Active Body does. This is an easy way to apply multiple modifiers to multiple bodies

Step 6: Brows

The eyebrows are similar to the eyes. Press SHIFT + A and add a UV sphere. Like before, move the mesh in object mode so it roughly lines up with the eyebrow. Scale it with S and rotate it with R.

Press TAB to go into edit mode and delete one half of the sphere. Make sure to leave the "equator". To do this, drag a box around the mesh to select all the vertices you want to delete, then press X. Select the equator and press E to extrude it. Using grab (G), rotate (R), and scale (S), build-out the rest of the eyebrow. When you get to the top of the eyebrow, scale everything to 0 and merge vertices. Move the eyebrow forward on Clippy so it sits in front of the body.

Get back into Object mode (TAB) and press SHIFT + D to duplicate it. Use G and R to position the eyebrow over on the other side. Press TAB to edit it and adjust it so it aligns with the other eyebrow.

Step 7: Boolean

If you're planning on gluing these together you need to make sure that you have a space in one body for the other one to glue into. To do that in Blender, you can use a Boolean modifier. Booleans can be finicky sometimes, but if you take your time you can usually make them work pretty well.

Select the body, then under the modifiers tab, add a Boolean modifier. The operation needs to be Difference, so it will remove one from the other. Select the body you want to be the "cutter". This forms the shape that will be removed from the body. You will need to repeat this process with every body.

One tip to make this easier is to name each body. You can double-click the body in the tree in the top-right, or edit the name under the Object Properties tab.

As you remove one body from another you can hide that body and you'll see the indent of it is missing from the actual paperclip body. If you look closely, you may notice that the edges aren't super clean. We need to add an Edge split again to force this edge to be nice and smooth. Modify the angle so it makes the new edges nice and crisp, but doesn't sharpen anything else on the model.

If you are wanting to print this all in one shot, change the Boolean Operation to Union. This will add the bodies together into one mesh instead of cutting one out of the other.

Step 8: All About That Base

To create the base, we're going add a circle. SHIFT + A > Mesh > Circle. Move it with G until is roughly around the bottom. Press TAB to go into edit mode. First we're going to go to extrude with E, and then scale to zero to bring the vertices into the centre. Then, right-click, Merge Vertices > By Distance to make it a flat face.

Press E to extrude down, then scale with S to give a bit of a bevel. E to extrude again. Scale the base to make it fit Clippy better and not be too thick. Move the base so the bottom of Clippy is embedded slightly. This will give you lots of area for glue and give you a good mounting point. This is the same process we did for the main body.

Add an:

Edge Split to make sharp edges
Subdivision Surface to smooth out the faces
Boolean to cut Clippy out of the base

Step 9: File Export

Now that Clippy is modeled, we need to export the meshes so we can 3D print him. If you used Union under your Boolean modifiers to combine him into a single mesh, you can just export him, but if you use Difference to split him into individial pieces that fit together, you will need to export each piece as its own STL file. Doing this manually is a pain. Luckily there is a setting that does it for you!

Select File > Export > STL. Under Batch Mode, make sure you choose Object. That will export each body as its own STL file, as .stl

Step 10: Printing

I printed the eyes in white, the eyebrows and pupils in black, and then the body and base in grey. You could print them all as one colour and paint them too. I'm using a Makerbot Replicator. An older printer, but still good. Print at 0.1mm layer thickness so you don't need to do much work to clean it up

Step 11: Cleanup

Once they are printed, use some 220 grit sandpaper and sand off all of the support material that might be still stuck to them. You can also use a knife and some patience as well, but of course be careful with the knife

Since 3D printers have a loose tolerance on prints, the pupils likely won't fit into the eyes right away. Keep sanding around the pupils until they shrink just enough to be press-fit into the eyes.

Step 12: Putting It All Together

Use some super glue to attach the pieces all together. I find that holding the pieces up to my monitor help me align these freeform parts accurately. If you were making a bigger model, you can use activator to solidify the super glue faster. I don't think that is needed for something this small.

Step 13: Hi There!

Overall this is a pretty simple project to make. It does touch on a lot of different tools and features inside a Blender as well as modelling for 3D printing, which can bring up a few quirks. Hopefully Clippy finds a nice new home on your desk!